U.S. patent number 7,400,355 [Application Number 10/618,699] was granted by the patent office on 2008-07-15 for image pickup apparatus and photometer.
This patent grant is currently assigned to Fujifilm Corporation. Invention is credited to Manabu Hyodo, Koji Ichikawa, Koichi Sakamoto, Masahiko Sugimoto, Kazuhiko Takemura, Masaya Tamaru.
United States Patent |
7,400,355 |
Tamaru , et al. |
July 15, 2008 |
Image pickup apparatus and photometer
Abstract
A received light quantity detection device where
high-sensitivity pixels and low-sensitivity pixels are formed is
used for photometry. It is possible to perform measurement over the
low range (for example, 0[EV] through 8[EV]with a single occasion
of photometry. In the case that both the high-sensitivity pixels
and the low-sensitivity pixels are saturated, it is possible to
perform further measurement over the high range (for example, 8[EV]
through 16[EV]) by narrowing the aperture or increasing the
electronic shutter speed for retried photometry with a retried
photometry. This reduces the time required to calculate a correct
exposure value on image pickup apparatus such as a camera.
Inventors: |
Tamaru; Masaya (Asaka,
JP), Sugimoto; Masahiko (Asaka, JP),
Sakamoto; Koichi (Asaka, JP), Hyodo; Manabu
(Asaka, JP), Takemura; Kazuhiko (Asaka,
JP), Ichikawa; Koji (Asaka, JP) |
Assignee: |
Fujifilm Corporation (Tokyo,
JP)
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Family
ID: |
30437424 |
Appl.
No.: |
10/618,699 |
Filed: |
July 15, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040012711 A1 |
Jan 22, 2004 |
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Foreign Application Priority Data
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Jul 15, 2002 [JP] |
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P.2002-205605 |
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Current U.S.
Class: |
348/364;
348/222.1; 348/229.1; 348/254; 348/297; 348/367; 348/E5.035 |
Current CPC
Class: |
H04N
5/2351 (20130101) |
Current International
Class: |
H04N
5/238 (20060101) |
Field of
Search: |
;348/221.1,229.1,254,275,315,362,364,367,222.1,296,297 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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62-147872 |
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Jul 1987 |
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JP |
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1-218178 |
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Aug 1989 |
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JP |
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6-189187 |
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Jul 1994 |
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JP |
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2000-125209 |
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Apr 2000 |
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JP |
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2000-316163 |
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Nov 2000 |
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JP |
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2002-57939 |
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Feb 2002 |
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JP |
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Other References
Y Wang et al., A High Dynamic Range CMOS APS Image Sensor, 2001
IEEE Workshop, Jun. 7-9, 2001. cited by examiner.
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Primary Examiner: Ho; Tuan
Assistant Examiner: Yoder, III; Chriss S
Attorney, Agent or Firm: Birch, Stewart, Kolasch &
Birch, LLP
Claims
What is claimed is:
1. An image pickup apparatus, comprising: a solid-state image
pickup device having high-sensitivity pixels and low-sensitivity
pixels, a photometric characteristic of an output of the
high-sensitivity pixels being different from that of the
low-sensitivity pixels, wherein the high-sensitivity pixels have a
first high-sensitivity exposure value ran e in which the function
before becoming saturated and a second high-sensitivity exposure
value range in which they function before becoming saturated and no
exposure value in the first hi-sensitivity exposure value range
overlaps with an exposure value in the second high-sensitivity
exposure value range, the low-sensitivity pixels have a first
low-sensitivity exposure value range in which they function before
becoming saturated and a second low-sensitivity exposure value ran
e in which the function before becoming saturated and no exposure
value in the first low-sensitivity exposure value range overlaps
with an exposure value in the second low-sensitivity exposure value
range, the exposure value at which the low-sensitivity pixels be in
to function in the first low-sensitivity exposure value range
coincides with the exposure value at which the high-sensitivity
pixels become saturated in the first high-sensitivity exposure
value range, and the exposure value at which the low-sensitivity
pixels begin to function in the second low-sensitivity exposure
value range coincides with the exposure value at which the
high-sensitivity pixels become saturated in the second
high-sensitivity exposure value range; control means for (i)
calculating an exposure value based on values of signal detected by
said high-sensitivity pixels operating in the first
high-sensitivity exposure value range and values of signal detected
by said low-sensitivity pixels operating in the first
low-sensitivity exposure value range, which are output from said
solid-state image pickup device in a first single instance of
photometry, and (ii) when a correct exposure value cannot be
obtained in the first single instance of photometry due to
saturation of both the high-sensitivity pixels and the
low-sensitivity pixels, calculating an exposure value based on
values of signal detected by said high-sensitivity pixels operating
in the second high-sensitivity exposure value range and values of
signal detected by said low-sensitivity pixels operating in the
second low-sensitivity exposure value range which are output from
said solid-state image pickup device in a second subsequent single
instance of photometry, where during each of the first and second
instance of photometry, aperture and electronic shutter speed are
not changed; and signal processing means for reading data of an
image picked up by said solid-state image pickup device and
processing according to the calculated exposure value.
2. The image pickup apparatus of claim 1, wherein each pixel
includes a high-sensitivity pixel and a low-sensitivity pixel.
3. An image pickup apparatus, comprising: image pickup means for
picking up a subject image; received light quantity detecting means
having high-sensitivity pixels and low-sensitivity pixels, a
photometric characteristic of an output of the high-sensitivity
pixels being different from that of the low-sensitivity pixels,
wherein the high-sensitivity pixels have a first high-sensitivity
exposure value range in which they function before becoming
saturated and a second high-sensitivity exposure value range in
which the function before becoming saturated and no exposure value
in the first high-sensitivity exposure value range overlaps with an
exposure value in the second high-sensitivity exposure value range,
the low-sensitivity pixels have a first low-sensitivity exposure
value range in which the function before becoming saturated and a
second low-sensitivity exposure value range in which they function
before becoming saturated and no exposure value in the first
low-sensitivity exposure value range overlaps with an exposure
value in the second low-sensitivity exposure value range, the
exposure value at which the low-sensitivity pixels begin to
function in the first low-sensitivity exposure value range
coincides with the exposure value at which the high-sensitivity
pixels become saturated in the first high-sensitivity exposure
value range, and the exposure value at which the low-sensitivity
pixels begin to function in the second low-sensitivity exposure
value range coincides with the exposure value at which the
high-sensitivity pixels become saturated in the second
high-sensitivity exposure value range; and control means for (i)
calculating an exposure value based on signal showing received
light quantity detected by said high-sensitivity pixels operating
in the first high-sensitivity exposure value range and signal
showing received light quantity detected by said low-sensitivity
pixels operating in the first low-sensitivity exposure value range,
which are output from said received light quantity detecting means
device in a first single instance of photometry, and (ii) when a
correct exposure value cannot be obtained in the first single
instance of photometry due to saturation of both the
high-sensitivity pixels and the low-sensitivity pixels calculating
an exposure value based on values of signal detected by said
high-sensitivity pixels operating in the second high-sensitivity
exposure value range and values of signal detected by said
low-sensitivity pixels operating in the second low-sensitivity
exposure value range which are output from said solid-state image
pickup device in a second subsequent single instance of photometry,
and controlling said image pickup means to pick up a subject image
according to the exposure value, where during each of the first and
second instance of photometry, aperture and electronic shutter
speed are not changed.
4. The image pickup apparatus of claim 3, wherein each pixel
includes a high-sensitivity pixel and a low-sensitivity pixel.
5. A photometer which calculates a exposure value of the image
pickup apparatus, comprising: received light quantity detecting
means having high-sensitivity pixels and low-sensitivity pixels, a
photometric characteristic of an output of the high-sensitivity
pixels being different from that of the low-sensitivity pixels,
wherein the high-sensitivity pixels have a first high-sensitivity
exposure value range in which they function before becoming
saturated and a second high-sensitivity exposure value range in
which they function before becoming saturated and no exposure value
in the first high-sensitivity exposure value range overlaps with an
exposure value in the second high-sensitivity exposure value range,
the low-sensitivity pixels have a first low-sensitivity exposure
value range in which they function before becoming saturated and a
second low-sensitivity exposure value range in which they function
before becoming saturated and no exposure value in the first
low-sensitivity exposure value range overlaps with an exposure
value in the second low-sensitivity exposure value range, the
exposure value at which the low-sensitivity pixels be in to
function in the first low-sensitivity exposure value range
coincides with the exposure value at which the hi -sensitivity
pixels become saturated in the first high-sensitivity exposure
value range, and the exposure value at which the low-sensitivity
pixels begin to function in the second low-sensitivity exposure
value range coincides with the exposure value at which the
high-sensitivity pixels become saturated in the second
high-sensitivity exposure value range; and calculating means for
(i) calculating the exposure value based on signal showing received
light quantity detected by said high-sensitivity pixels operating
in the first high-sensitivity exposure value range and signal
showing received light quantity detected by said low-sensitivity
pixels operating in the first low-sensitivity exposure value range,
which are output from the received light quantity detecting means
device in a first single instance of photometry, and (ii) when a
correct exposure value cannot be obtained in the first single
instance of photometry due to saturation of both the
high-sensitivity pixels and the low-sensitivity pixels, calculating
an exposure value based on values of signal detected by said
high-sensitivity pixels operating in the second high-sensitivity
exposure value range and values of signal detected by said
low-sensitivity pixels operating in the second low-sensitivity
exposure value range, which are output from said solid-state image
pickup device in a second subsequent single instance of photometry,
where during each of the first and second instance of photometry,
aperture and electronic shutter speed are not changed.
6. The photometer of claim 5, wherein each pixel includes a
high-sensitivity pixel and a low-sensitivity pixel.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to image pickup apparatus such as a
camera and a photometer, and in particular to image pickup
apparatus and a photometer which can perform photometry with a wide
dynamic range.
2. Description of the Related Art
A photometer described in JP-A-6-130462 is known as a related art,
which is mounted on image pickup apparatus such as a digital still
camera. The conventional photometer alternately performs photometry
where the charge storage time of photoreceptors such as CCDs is
longer (that is, photometry which focuses on low intensity of
light) and photometry where the charge storage time of a
photoreceptor is shorter (photometry which focuses on high
intensity of light) so as to allow photometry with a wide dynamic
range.
The conventional photometer alternately performs the
high-intensity-oriented photometry and the low-intensity-oriented
photometry to allow photometry with a wide dynamic range. However,
there is a problem that it takes time to determine an exposure
value after the release button is touched (depressed lightly),
since the photometer frequently changes the charge storage time to
perform photometry.
SUMMARY OF THE INVENTION
An object of the invention is to provide image pickup apparatus and
a photometer which can perform photometry with a wide dynamic range
in a brief period of time while reducing the number of repetitions
of photometry.
The invention provides an image pickup apparatus having a
solid-state image pickup device where high-sensitivity pixels and
low-sensitivity pixels are formed, control means for calculating an
exposure value based on values of signal detected by the
high-sensitivity pixels and values of a signal detected by the
low-sensitivity pixels, which are output from the solid-state image
pickup device, and signal processing means for reading data of an
image picked up by the solid-state image pickup device and
processing according to the exposure value.
With this configuration, it is possible to obtain photometry data
which are picked up with various detection sensitivities with a
single occasion of photometry. Even when the high-sensitivity
pixels are saturated and photometry data is unavailable from the
high-sensitivity pixels, photometry data from the low-sensitivity
pixels is available as long as the low-sensitivity pixels remain
unsaturated. This allows calculation of a correct exposure value in
a brief period of time.
The invention also provides an image pickup apparatus having image
pickup means for picking up a subject image, received light
quantity detecting means where high-sensitivity pixels and
low-sensitivity pixels are formed, and control means for
calculating an exposure value based on signal showing received
light quantity detected by the high-sensitivity pixels and signal
showing received light quantity detected by the low-sensitivity
pixels, which are output from the received light quantity detecting
means, and controlling the image pickup means to pick up a subject
image according to the exposure value.
With this configuration, it is also possible to obtain photometry
data which are picked up with various detection sensitivities with
a single occasion of photometry. Even when the high-sensitivity
pixels are saturated and photometry data is unavailable from the
high-sensitivity pixels, photometry data from the low-sensitivity
pixels is available as long as the low-sensitivity pixels remain
unsaturated. This allows calculation of a correct exposure value in
a brief period of time.
The invention also provides a photometer which calculates a
exposure value of the image pickup apparatus having received light
quantity detecting means where high-sensitivity pixels and
low-sensitivity pixels are mounted, and calculating means for
calculating the exposure value based on signal showing received
light quantity detected by the high-sensitivity pixels and signal
showing received light quantity detected by the low-sensitivity
pixels, which are output from the received light quantity detecting
means.
With this configuration, it is also possible to obtain photometry
data which are picked up with various detection sensitivities with
a single occasion of photometry. Even when the high-sensitivity
pixels are saturated and photometry data is unavailable from the
high-sensitivity pixels, photometry data from the low-sensitivity
pixels is available as long as the low-sensitivity pixels remain
unsaturated. This allows calculation of a correct exposure value in
a brief period of time.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a digital still camera according to an
embodiment of the invention;
FIG. 2 shows a pixel arrangement of the solid-state image pickup
device shown in FIG. 1;
FIG. 3 is a graph showing the relationship between the signal of
the solid-state image pickup device shown in FIG. 2 and the
exposure;
FIG. 4 is a diagram of photometry lines of the solid-state image
pickup device shown in FIG. 2;
FIG. 5 is a flowchart showing the exposure value calculation
processing performed by the CPU shown in FIG. 1;
FIG. 6 is a block division diagram showing the photometry areas of
the solid-state image pickup device shown in FIG. 1;
FIG. 7 shows a pixel arrangement of the solid-state image pickup
device mounted on a digital still camera according to another
embodiment of the invention;
FIG. 8 is a graph showing the relationship between the signal of
the solid-state image pickup device shown in FIG. 7 and the
exposure; and
FIG. 9 is a diagram of photometry lines of the solid-state image
pickup device shown in FIG. 7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the invention will be described referring to
drawings.
FIG. 1 is a block diagram of a digital still camera according to an
embodiment of the invention. The digital still camera has an image
pickup lens 10, a solid-state image pickup device 11, a diaphragm
12 provided between the image pickup lens 10 and the solid-state
image pickup device 11, an infrared filter 13, an optical low-pass
filter 14, a CPU 15 for controlling the entire digital still
camera, a light-receiving section 17 and a light-emitting section
16 for a flashlight, a lens driving section 18 for adjusting the
position of the image pickup lens 10, a diaphragm driving section
19 for adjusting the diaphragm 12, an image pickup device driving
section 20 for operating the solid-state image pickup device 11, an
analog signal processor 22 for performing analog signal processing
after capturing an output signal of the solid-state image pickup
device 11, and an A/D converter 23 for converting an output signal
of the analog signal processor 22 to a digital signal.
The CPU 15 controls the lens driving section 18 to position the
image pickup lens 10 at a focal position. The CPU 15further drives
and controls the solid-state image pickup device 11 by controlling
the image pickup device driving section 20. As a result, the
solid-state image pickup device 11 outputs a chrominance signal of
a subject image picked up through the image pickup lens 10. An
instruction signal by a user is input to the CPU 15 via an
operating section 21. The CPU 15 performs various types of control
in accordance with the instruction. The solid-state image pickup
device 11 is a CCD where honeycomb-shaped pixels are arranged, a
Bayer type CCD, or a CMOS sensor.
The digital processing system of the digital still camera has a
memory controller 25 connected to a main memory 24, a digital
signal processor 26, a compression/decompression processor 27 for
compressing a picked-up image to a JPEG image and decompressing a
compressed image, an integrator 28 for totalizing photometry data,
an external memory controller 30 to which a detachable recording
medium 29 is connected, and a display controller 32 to which an LCD
31 mounted on the rear of a camera is connected. These components
are interconnected via a control bus 33 and a data bus 34 and
controlled by an instruction from the CPU 15.
The digital signal processor 26, the analog signal processor 22 and
the A/D converter 23 shown in FIG. 1 may be respectively mounted on
a digital still camera as separate circuits. However, these
components are preferably manufactured on the same semiconductor
substrate as the solid-state image pickup device 11 by using the
LSI manufacturing technology to form single solid-state image
pickup apparatus.
The aforementioned digital still camera performs focusing and
calculates a correct exposure when a release button (not shown) is
touched (depressed lightly) by a user before the release button is
depressed far enough and an instruction for picking up an image is
input.
When the correct exposure is calculated, the CPU 15 adjusts the
electronic shutter speed and the aperture of the diaphragm 12 in a
variable way while the release button is depressed lightly,
processes the output signal of the solid-state image pickup device
11 obtained while the release button is depressed lightly, and
calculates the correct exposure based on the photometry data
totalized by the integrator 28 by way of a well-known method. The
CPU 15 sets the electronic shutter speed and the aperture of the
diaphragm 12 which are based on the correct exposure, picks up an
image when the release button is depressed far enough, processes
the data of the image, and stores the processed image data onto the
recording medium 29.
FIG. 2 shows a pixel arrangement of the solid-state image pickup
device 11 mounted on the digital still camera according to the
embodiment. High-sensitivity pixels 51 shown with a large octagon
and low-sensitivity pixels 52 shown with a small circle are formed
on the same semiconductor substrate of the solid-state image pickup
device 11. As a result, an image picked up with the
high-sensitivity pixels 51 and an image picked up with the
low-sensitivity pixels 52 are synthesized as a single image to form
a single still image with a wide dynamic range.
A large number of photodiodes in the same dimension and shape are
formed on the solid-state image pickup device 11. The
high-sensitivity pixels 51 and the low-sensitivity pixels 52 are
discriminated depending on the size of the area of a micro-lens or
a color filter provided in front of each photodiode.
FIG. 3 shows a general tendency of a signal level with respect to
the exposure of each of the high-sensitivity signal H obtained from
the high-sensitivity pixels 51 and the low-sensitivity signal L
obtained from the low-sensitivity pixels 52. According to the
solid-state image pickup device 11 shown in FIG. 2, the
high-sensitivity pixels 51 and the low-sensitivity pixels 52 have
photodiodes in the same dimension and shape, so that both types of
pixels have the same value "4n" of the saturation signal level.
However, the light-receiving area is different. The
high-sensitivity pixels 51 are saturated with a received light
quantity "m" while the low-sensitivity pixels 52 are saturated with
a received light quantity "16"m in the example shown.
FIG. 4 is a diagram of photometry lines of the solid-state image
pickup device 11 shown in FIG. 2. The vertical axis shows detected
values (obtained as an average of values of the signal detected by
a large number of pixels) while the horizontal axis shows exposure
values (EV).
The photometry line diagram of the high-sensitivity pixels 51 of
the solid-state image pickup device 11 shows the characteristic
line A, the characteristic line C, while the photometry line
diagram of the low-sensitivity pixels 52 shows the characteristic
line B, the characteristic line D. It is thus possible to perform a
measurement over the range of 0[EV] through 8[EV] using the
characteristic line A and the characteristic line B with a single
occasion of photometry. In the case that both the high-sensitivity
pixels 51 and the low-sensitivity pixels 52 are saturated, it is
possible to perform further measurement over the range of 8[EV]
through 16[EV] using the characteristic line C and the
characteristic line D by narrowing the aperture or increasing the
electronic shutter speed with retried photometry.
FIG. 5 is a flowchart showing the exposure value calculation
processing performed by the CPU 15. First, the CPU 15 sets the
aperture of the diaphragm 12 and the electronic shutter speed of
the solid-state image pickup device 11 (step S1). The CPU 15 then
acquires photometry data from the image pickup signal received from
the solid-state image pickup device 11 (step S2). The entire
exposure surface of the solid-state image pickup device 11 is
divided into 8.times.8=64 blocks and the photometry data is
acquired for each of these blocks.
As mentioned earlier, the solid-state image pickup device 11 of the
embodiment is equipped with the high-sensitivity pixels 51 and the
low-sensitivity pixels 52. Therefore, it is possible to obtain,
with single photometry timing, two types of photometry data which
are picked up with different sensitivities. Even when the
high-sensitivity pixels 51 are saturated and are no longer capable
of performing photometry, it is possible to use the photometry data
from the low-sensitivity pixels 52 to calculate the exposure.
In step S3, the CPU 15 determines whether or not correct photometry
data is obtained for all blocks. In the case that correct data is
not obtained for all blocks, execution proceeds to step S4, where
the CPU 15 sets the aperture and the electronic shutter speed
again, and acquires photometry data from the image pickup signal
received from the solid-state image pickup device 11 for a second
time (step S2).
In the case that it is determined that, in step S3, correct data is
obtained for all blocks, execution proceeds to step S5, where the
CPU 15 calculates an exposure value based on the photometry data on
all blocks to terminate the exposure value calculation
processing.
In this way, the digital still camera of the embodiment obtains,
with a single occasion of photometry, two types of photometry data
which are picked up with different sensitivities. This reduces the
number of repetitions of a series of steps S2, S3, S4 and S2 back
again, thus allows calculation of a correct exposure in a brief
period of time.
FIG. 7 shows a pixel arrangement of the solid-state image pickup
device 11 mounted on a digital still camera of another embodiment.
In the solid-state image pickup device of the another embodiment,
each pixel 60 is divided into the area for high-sensitivity pixels
61 and the area for low-sensitivity pixels 62. The signal charge of
the high-sensitivity pixels 61 and the signal charge of the
low-sensitivity pixels 62 are separately read onto a vertical
transfer path and transferred thereon.
FIG. 8 shows a general tendency of a signal level with respect to
the exposure of each of the high-sensitivity signal H read from the
high-sensitivity pixels 61 and the low-sensitivity signal L read
from the low-sensitivity pixels 62. In the example shown, the level
of saturation of the high-sensitivity signal H is "4n" which is
four times as high as the level of saturation of the
low-sensitivity signal L which is "n". The light quantity where the
signal level reaches the saturation level is "m" for the
high-sensitivity pixels 61, while the light quantity "2m" for the
low-sensitivity pixels 62, which is double the former "m".
FIG. 9 is a diagram of photometry lines of the solid-state image
pickup device shown in FIG. 7. The vertical axis shows detected
values, while the horizontal axis shows exposure values (EV). The
photometry line diagram of the high-sensitivity pixels 61 of the
solid-state image pickup device according to the embodiment shows
the characteristic line A, the characteristic line C, while the
photometry line diagram of the low-sensitivity pixels 62 shows the
characteristic line B, the characteristic line D. It is possible to
perform measurement over the range of 0[EV] through 6[EV] using the
characteristic line A and the characteristic line B with a single
occasion of photometry. In the case that both the high-sensitivity
pixels 61 and the low-sensitivity pixels 62 are saturated, it is
possible to perform further measurement over the range of 6 [EV]
through 10 [EV] using the characteristic line C and the
characteristic line D on a single occasion of photometry by
narrowing the aperture or increasing the electronic shutter speed
with retried photometry.
The digital still camera where such a solid-state image pickup
device is mounted follows the same procedure as mentioned referring
to FIG. 5 to perform exposure value calculation processing. In this
case also, it is possible to obtain, with a single occasion of
photometry, two types of photometry data which are picked up with
different sensitivities. This reduces the number of repetitions of
photometry, thus allows calculation of a correct exposure in a
brief period of time.
While the digital still camera using the output signal of a
solid-state image pickup device in photometry has been described in
the embodiments, a received light quantity detection device
equipped with both high-sensitivity pixels and low-sensitivity
pixels may be mounted on image pickup apparatus apart from the
solid-state image pickup device so as to obtain photometry data
from the output signal of the received light quantity detection
device. In this case, the image pickup means is not limited to a
solid-state image pickup device but may be a silver halide film
camera.
According to the embodiments, both output of high-sensitivity
pixels and output of low-sensitivity pixels are used for
photometry, so that it is possible to perform photometry with a
wide dynamic range in a brief period of time.
* * * * *